Electrochromic polymer material

ABSTRACT

Provided are (1) a terpyridine monomer that has a strong ability to coordinate with metal atoms, and (2) a polymer material that can be readily switched between a colored state and a colorless state by controlling the electrical potential applied to it and that can be processed. 
     A bis-terpyridine monomer of a first invention comprises a first terpyridyl substituent (A), a second terpyridyl substituent (B), and a spacer that contains at least one benzene ring and links the substituents (A) and (B). 
     A polymer material of a second invention comprises a bis-terpyridine derivative derived from the monomer according to the first invention, a metal ion and a counter anion, or comprise first to Nth bis-terpyridine derivatives (N is an integer of 2 or greater), first to Nth metal ions (N is an integer of 2 or greater) and first to Nth counter anions (N is an integer of 2 or greater).

TECHNICAL FIELD

The present invention relates to an electrochromic polymer material thatcan be readily switched between a colored state and a colorless state bycontrolling the electrical potential applied to it (Inventions relatedto this polymer material are referred to as a “second group ofinvention,” hereinafter.)

BACKGROUND ART

In recent years, functional materials with novel properties have beenintensively studied. In particular, organic polymers combined withmetals are expected to provide new optical, electronic, magnetic,catalytic and various other functions. Such organic polymer-metalcomposite materials are finding many applications in light-emittingdevices, energy-converting materials, drug delivery, sensors,high-performance catalysts, solar batteries and other technical fields.

Organic polymers are soft materials that have spaghetti-like molecularstructures with an extremely high degree of freedom. Since organicpolymers have a distribution of molecular weights, composites of organicpolymers and metals are generally provided in the form of merestatistical mixtures. Thus, coordination polymers, organic polymers thatcan coordinate with metals, are needed to obtain organic polymer-metalcomposite materials that exhibit novel useful functions. A techniqueusing bipyridyl derivatives as such coordination polymers is known (See,for example, Patent Document 1).

Light modulation devices, display devices and other optical devicesusing electrochromic materials have also become the subjects ofintensive studies, recently. Such electrochromic materials includeinorganic materials, such as tungsten oxide, organic materials, such asviologens, and conductive polymer materials.

It is desirable that these electrochromic materials, when used in lightmodulation devices, display devices and other optical devices, can bereadily switched between the colored state and the colorless state.Although inorganic materials and organic materials can achieve favorablecolorless state (transparency), their colored state is undesirable.Conductive polymer materials, on the other hand, can achieve desirablecolored state, but their colorless state (transparency) is undesirable.This is because the conductivity of the conductive polymer materialsresults from the n-electron conjugated system. Non-doped conductivepolymer materials thus absorb significant amounts of light and exhibitcolors such as dark yellow, red, green and deep blue.

An electrochromic display device technology has been developed that usesa conductive polymer material that has overcome the problem of theundesirable colorless state (See, Patent Document 2). The electrochromicdisplay device used in this technology comprises a first transparentelectrode, a graft conductive polymer layer arranged in contact with thefirst transparent electrode, an electrolyte layer arranged in contactwith the graft conductive polymer layer, and a second electrode withwhich the first transparent electrode sandwiches the graft conductivepolymer layer and the electrolyte layer. The graft conductive polymerlayer is formed of a conductive polymer backbone linked to a conjugatedmolecular pendant via a metal or a metal ion.

The conjugated molecular pendant causes the conductive polymer materialto change its unique state of π-electron bonding or π-π* transitionenergy. This in turn causes the light absorption band of the conductivepolymer material to shift to a shorter or longer wavelength range. As aresult, the light absorption in the visible range is decreased to anunnoticeable degree and the conductive polymer material becomestransparent.

REFERENCE DOCUMENT

-   Patent Document 1: JP-A-2005-200384-   Patent Document 2: JP-A-2004-20928

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

Patent Document 1 describes an organic polymer-metal composite materialwhich is a polymer in which monomer units are linked by metal atoms. Inthis polymer, the binding between the metal atoms and the bipyridylderivative may weaken when the valency of the metal atoms changes or thesurrounding environment, such as acidity, changes. As a result, thepolymer may break down. Thus, there is a need for a coordination polymerthat has a strong ability to coordinate with metal atoms.

As opposed to the organic polymer-metal composite material described inPatent Document 1, a polymer in which the polymer backbone enclosesmetal atoms is expected to not only have increased strength, but alsohave increased interaction with the metal atoms.

Accordingly, (i) an object of the first group of the present inventionis to provide a terpyridine monomer suitable for the synthesis of apolymer that can strongly coordinate with metals, as well as a processfor producing the monomer.

The graft conductive polymer layer described in Patent Document 2 issynthesized by the electrolytic polymerization of a monomer. Oncesynthesized, however, this graft conductive polymer layer is difficultto be re-processed. Thus, there is a need for an electrochromic polymermaterial that can be readily processed.

Accordingly, (ii) an object of the second group of the present inventionis to provide a polymer material that can be readily switched between acolored state and a colorless state by controlling the electricalpotential applied to it and that can be readily processed, as well as anelectrochromic device using such a polymer material.

Means for Solving the Problem

(i) The object of the first group of the present invention is achievedby the following features (1) through (11):

(1) A bis-terpyridine monomer, comprising a first terpyridyl substituent(A), a second terpyridyl substituent (B) and a spacer that contains atleast one benzene ring and links the substituents (A) and (B), thebis-terpyridine monomer being represented by the following formula (10):

where X¹ is a halogen; and R¹, R², R³ and R⁴ are each independently ahydrogen atom, an aryl group or an alkyl group.

(2) The bis-terpyridine monomer, wherein the second terpyridylsubstituent (B) in the above formula (10) further includes a halogen X²,the bis-terpyridine monomer being represented by the following formula(11):

where X² is a halogen that may or may not be identical to or differentfrom X¹.

(3) The bis-terpyridine monomer, wherein the first terpyridylsubstituent (A) in the above formula (11) further includes a halogen X³,the bis-terpyridine monomer being represented by the following formula(12):

where X³ is a halogen that may or may not be identical to or differentfrom X¹ and/or X².

(4) The bis-terpyridine monomer, wherein the second terpyridylsubstituent (B) in the above formula (12) further includes a halogen X⁴,the bis-terpyridine monomer being represented by the following formula(13):

where X⁴ is a halogen that may be identical to or different from X¹, X²and/or X³.

(5) The spacer R in each of the above formulas may be selected from thegroup consisting of the following formulas (3) through (6):

(6) The X¹ in each of the above formulas may be positioned adjacent tothe nitrogen atom of the corresponding terminal pyridine.

(7) The X¹ and X² in each of the above formulas may be each positionedadjacent to the nitrogen atom of each corresponding terminal pyridine.

(8) The X¹, X² and X³ in each of the above formulas may be eachpositioned adjacent to the nitrogen atom of each corresponding terminalpyridine.

(9) The X¹, X², X³ and X⁴ in each of the above formulas may be eachpositioned adjacent to the nitrogen atom of each corresponding terminalpyridine.

(10) A process for producing a bis-terpyridine monomer, comprising thesteps of:

refluxing a 2-acetylpyridine derivative of the formula (7) and a2-acetylpyridine derivative of the formula (14) with iodine andpyridine;

reacting an aryldialdehyde derivative of the formula (15) with 2equivalents of at least one 2-acetylpyridine derivative selected fromthe group represented by the formula (16) in an aqueous alkalinesolution; and

refluxing the reaction product of the refluxing step and the reactionproduct of the reacting step with ammonium acetate and methanol:

where X¹ is a halogen; R¹, R², R³ and/or R⁴ are each independently ahydrogen atom, an aryl group or an alkyl group; and R is a spacercontaining at least one benzene ring.

(11) The process according to (10), wherein the spacer R is selectedfrom the group consisting of the following formulas (3) through (6):

(ii) The object of the second group of the present invention is achievedby the following features (12) through (22):

(12) An electrochromic polymer material according to the presentinvention, including a bis-terpyridine derivative, a metal ion and acounter ion, the electrochromic polymer material being represented bythe following formula (22):

where M is the metal ion; R is a spacer that contains a carbon atom or ahydrogen atom, or directly links the terpyridyl groups to each other;R¹, R², R³ and R⁴ are each independently a hydrogen atom, an aryl groupor an alkyl group; and n is an integer of 2 or greater indicating thedegree of polymerization.

(13) An electrochromic polymer material according to the presentinvention, including first to Nth bis-terpyridine derivatives (N is aninteger of 2 or greater), first to Nth metal ions (N is an integer of 2or greater) and first to Nth counter anions (N is an integer of 2 orgreater), the electrochromic polymer material being represented by thefollowing formula (23):

where M¹, . . . , M^(N) are first to Nth different metal ions,respectively (N is an integer of 2 or greater); R¹, . . . , R^(N) areeach independently a spacer that contains a carbon atom or a hydrogenatom, or directly links corresponding terpyridyl groups to each other (Nis an integer of 2 or greater); R¹ ₁, . . . , R¹ _(N), R² ₁, . . . , R²_(N), R³ ₁, . . . , R³ _(N), R⁴ ₁, . . . , R⁴ _(N) are eachindependently a hydrogen atom, an aryl group or an alkyl group (N is aninteger of 2 or greater); n¹, . . . , n^(N) are each an integer of 2 orgreater indicating the degree of polymerization; and the first to Nthcounter anions are identical to, different from, or partly equal to oneanother.

(14) The first to Nth metal ions may be independently selected from thegroup consisting of iron ion, cobalt ion, nickel ion and zinc ion.

(15) A process for producing the polymer material according to (12),comprising the step of refluxing a bis-terpyridine derivative of theformula (24) and a metal salt in acetic acid and methanol:

where R is a spacer that contains a carbon atom or a hydrogen atom, ordirectly links the terpyridyl groups to each other; R¹, R², R³ and R⁴are each independently a hydrogen atom, an aryl group or an alkyl group;and n is an integer of 2 or greater indicating the degree ofpolymerization.

(16) A process for producing the polymer material according to (13),comprising the steps of: refluxing each of the first to Nthbis-terpyridine derivatives of the formula (25) (N is an integer of 2 orgreater) and each of the first to Nth metal salts (N is an integer of 2or greater) in acetic acid and methanol; and mixing together first toNth reaction products obtained in the refluxing step (N is an integer of2 or greater):

where R¹, . . . , R^(N) are each independently a spacer that contains acarbon atom or a hydrogen atom, or directly links correspondingterpyridyl groups to each other (N is an integer of 2 or greater); R¹ ₁,. . . , R¹ _(N), R² ₁, . . . , R² _(N), R³ ₁, . . . , R³ _(N), R⁴ ₁, . .. , R⁴ _(N) are each independently a hydrogen atom, an aryl group or analkyl group (N is an integer of 2 or greater); and n¹, . . . , n^(N),are each an integer of 2 or greater indicating the degree ofpolymerization.

(17) The process according to (16), wherein the first to Nth metal saltseach include a combination of a metal ion selected from the groupconsisting of iron ion, cobalt ion, nickel ion and zinc ion and acounter anion selected from the group consisting of acetate ion,tetrafluoroborate ion, polyoxometalate and combinations thereof.

(18) The process according to (16), wherein the spacers R¹, . . . ,R^(N) are each independently an aryl group or an alkyl group.

(19) The process according to (18), wherein the aryl group or alkylgroup further contains an oxygen atom or an sulfur atom.

(20) The process according to (18), wherein the aryl group is selectedfrom the group consisting of the following formulas (3) through (6):

(21) An electrochromic device, comprising a first transparent electrodesubstrate, a second transparent electrode substrate, and the polymermaterial according to (12) above arranged between the first transparentelectrode substrate and the second transparent electrode substrate.

(22) An electrochromic device, comprising a first transparent electrodesubstrate, a second transparent electrode substrate, and the polymermaterial according to (13) or (14) above arranged between the firsttransparent electrode substrate and the second transparent electrodesubstrate.

ADVANTAGES OF THE INVENTION

The bis-terpyridine monomer according to the first group of the presentinvention includes halogens X¹ and X⁴ at specific positions. Suchhalogens are readily substituted with other substituents. Thus, themonomer can be used to synthesize derivatives having varioussubstituents. Furthermore, the monomer can readily undergo condensationto form polymers that have strong ability to coordinate with metals, theability that has never been achieved by conventional polymer materials.

In the polymer material derived from the monomer according to the secondgroup of the present invention, electrical charge can move between themetal ion M and the bis-terpyridine derivative, a ligand. Thus, bycontrolling the electrical potential applied to the polymer material,the metal ion will readily change its valency, causing the polymermaterial to switch from its colored state to an ideal transparent state.In addition, the polymer material can achieve a desired color by usingdifferent combinations of metal ions and ligand, or by using differentcombinations of metal ions and counter anions. Furthermore, the polymermaterial of the present invention is soluble in various solvents and cantherefore be processed after its synthesis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a production process of a bis-terpyridinemonomer.

FIG. 2 is a schematic diagram of an organic polymer-metal compositematerial according to the present invention.

FIG. 3 is a schematic diagram of the polymer material according toEmbodiment 1.

FIG. 4 is a schematic diagram of the polymer material according toEmbodiment 2.

FIG. 5 is a schematic diagram of an electrochromic device according toEmbodiment 3.

FIG. 6 is a cyclic voltammogram of FeMEPE.

FIG. 7 is a diagram showing color change of FeMEPE.

FIG. 8 is absorption spectra of FeMEPE in the UV-visible range.

FIG. 9 is a diagram showing the switching characteristic of the peakintensity at a wavelength of 580 nm.

FIG. 10 is a cyclic voltammogram of CoMEPE.

FIG. 11 is absorption spectra of CoMEPE in the UV-visible range.

FIG. 12 is a diagram showing the switching characteristic of the peakintensity at a wavelength of 520 nm.

FIG. 13 is absorption spectra of CoMEPE-FeMEPE in the UV-visible range.

FIG. 14 shows diagrams showing the switching characteristic of the peakintensity at wavelengths of 520 nm and 580 nm, respectively.

FIG. 15 is absorption spectra of CoMEPE′-FeMEPE′ in the UV-visiblerange.

EXPLANATION OF REFERENCE SYMBOLS

-   -   300: electrochromic device    -   310: first transparent electrode    -   320: polymer material    -   330: second transparent electrode    -   340: polymer solid electrolyte

BEST MODE FOR CARRYING OUT THE INVENTION

Several embodiments of the first group of the present invention will nowbe described with reference to FIGS. 1 and 2.

Embodiment 1

Bis-terpyridine monomers of the present invention are represented by thefollowing formula (10):

For comparison, terpyridine monomers are shown below by the formulas (1)and (2):

(1) A bis-terpyridine monomer includes a first terpyridyl substituent(A), a second terpyridyl substituent (B) and a spacer R that links thefirst terpyridyl substituent (A) and the second terpyridyl substituent(B).

X¹ in the first terpyridyl substituent (A) is a halogen, which ispreferably bromine, chlorine or iodine, and more preferably bromine. X¹provides the bis-terpyridine monomer with high reactivity. While X¹ maybe positioned at any position of the terminal pyridine that contains X¹,it is preferably positioned adjacent to the nitrogen atom of theterminal pyridine.

R¹, R², R³ and R⁴ are each independently a hydrogen atom, an aryl groupor an alkyl group, Examples include, but are not limited to, methylgroup, ethyl group, n-butyl group, t-butyl group, phenyl group and tolylgroup. The aryl group or alkyl group may have additional substituents,including alkyl groups, such as methyl group, ethyl group and hexylgroup, alkoxy groups, such as methoxy group and butoxy group, andhalogen groups, such as chlorine and bromine.

The spacer R includes at least one benzene ring and may be an aryl groupor an alkyl group. The spacer R is preferably selected from the groupconsisting of the formulas (3) through (6) shown below. The spacer Rserves to raise the breakdown point (melting point) and thus improve thetemperature resistance of the resulting terpyridine monomer. The spacersshown below are each a conjugated aryl group and can readily donate oraccept electrons. Terpyridine monomers containing these aryl groups areuseful as electronic materials. Also, these aryl groups have morestructurally defined skeletons than alkyl groups and therefore allowcontrol of the orientation of terpyridine monomers. Thus, the arylgroups are more advantageous in designing materials than alkyl groups.

The second terpyridyl substituent (B) in the bis-terpyridine monomershown by the formula (10) may contain an additional halogen X², as shownby the following formula (11)

The additional halogen X² is bromine, chlorine or iodine, and mostpreferably bromine. It may or may not be identical to X¹. While X² maybe positioned at any position of the terminal pyridine that contains X²,it is preferably positioned adjacent to the nitrogen atom of theterminal pyridine. This allows the bis-terpyridine monomer to becondensed to form a straight-chained polymer.

The first terpyridyl substituent (A) in the bis-terpyridine monomershown by the formula (11) may contain an additional halogen X³, as shownby the following formula (12):

The additional halogen X³ is bromine, chlorine or iodine, and mostpreferably bromine. It may or may not be identical to X¹ and/or X².While X³ may be positioned at any position of the terminal pyridine thatcontains X³, it is preferably positioned adjacent to the nitrogen atomof the terminal pyridine. This allows the bis-terpyridine monomer to becondensed to form a straight-chained polymer.

The second terpyridyl substituent (B) in the bis-terpyridine monomershown by the formula (12) may contain an additional halogen X⁴, as shownby the following formula (13):

The additional halogen X⁴ is bromine, chlorine or iodine, and mostpreferably bromine. It may or may not be identical to X¹, X² and/or X³.While X⁴ may be positioned at any position of the terminal pyridine thatcontains X⁴, it is preferably positioned adjacent to the nitrogen atomof the terminal pyridine. This allows the bis-terpyridine monomer to becondensed to form a straight-chained polymer.

No previous studies have suggested the bis-terpyridine monomers shown bythe formulas (10) through (13) that include the halogens or substituentsshown by X¹ through X⁴ that pose a hindrance to the coordination ofmetal atoms to the terpyridine group. Nor have any studies anticipatedpolymers that enclose metal atoms, which will be described later in isEmbodiment 3. The bis-terpyridine monomers of Embodiment 1, whichinclude two terpyridyl groups, can enclose more metal atoms than theterpyridine monomers that include only one terpyridyl group, which areshown as reference in the formula (1). Thus, the resulting polymer isexpected to have increased interaction with the metal atoms, making thepolymer applicable to novel devices.

A process for producing the bis-terpyridine monomer of the formula (10)will now be described.

The process for producing the bis-terpyridine monomer is shown in FIG.1.

The process is described step by step in the following.

Step S210: A 2-acetylpyridine derivative of the formula (7) and a2-acetylpyridine derivative of the formula (14) are refluxed with iodineand pyridine. This gives a product 210 and a product 220, each apyrimidium salt.

Step S220: An aryldialdehyde derivative of the formula (15) is reactedwith at least one 2-acetylpyridine derivative selected from the grouprepresented by the formula (16), in an alkaline solution. The alkalinesolution can enolize the 2-acetylpyridine derivative. The reaction canbe carried out by stirring the reaction mixture for at least 24 hours atroom temperature. Specifically, the aryldialdehyde derivative is reactedwith 2 equivalents of the 2-acetylpyridine derivative. This step gives aproduct 230, a product 240 or a product 250.

Step S230: The products obtained in Step S210 and Step S220 are refluxedin ammonium acetate and methanol. The products 210 and 220 react withone of the products 230 through 250 to form a bis-terpyridine monomer200.

In this process, X¹ is a halogen, preferably bromine, chlorine oriodine, and most preferably bromine. While X¹ may be positioned at anyposition of the terminal pyridine that contains X¹, it is preferablypositioned adjacent to the nitrogen atom of the terminal pyridine.

The 2-acetylpyridine derivative of the formula (14) may contain anadditional halogen X². The halogen X² may or may not be identical to X¹and is preferably bromine. While X² may be positioned at any position ofthe terminal pyridine that contains X², it is preferably positionedadjacent to the nitrogen atom of the terminal pyridine. X¹ and X² arehorizontally arranged in the final product 200 obtained in Step 230.

Likewise, the 2-acetylpyridine derivatives of the formula (16) may eachcontain additional halogens X³ and/or X⁴. The halogens X¹, X², X³ and X⁴may be identical to different from, or partly equal to one another andare each preferably bromine. While halogens X³ and X⁴ may be positionedat any position of the pyridines that contain them, they are preferablypositioned adjacent to the nitrogen atom of the pyridines. All of thehalogens are horizontally arranged in the final product 200.

The bis-terpyridine monomer of the present invention, which includeshalogens in at least one of its two terpyridine groups, can be used tosynthesize not only coordination polymers with metal atoms, but alsopolymers in which the polymer backbone can enclose metal atoms.

Embodiment 2

Applications of the monomer obtained in Embodiment 1 will now bedescribed.

The monomer obtained in Embodiment 1 can be used to make a bis-typepolymer shown by the formula (19) below. In the formula (19), n is aninteger of 2 or greater. For comparison, a terpyridyl polymer (18)derived from the formula (1) is shown together as a reference example.

The polymer of the formula (19) and the polymer of the formula (18) ofthe reference example are obtained by the condensation of the monomerobtained in Embodiment 1 in the presence of a nickel catalyst or acopper catalyst. The nickel catalyst may be a mixture ofbis(1,5-cyclooctadiene)nickel and 2,2′-bipyridyl ortetrakis(triphenylphosphine) nickel. The copper catalyst may be a copperpowder.

The condensation reaction can be carried out by dissolving the monomerin a solvent (preferably an organic solvent) and leaving the solution inan atmosphere of inactive gas, such as nitrogen and argon. The solutionmay be dehydrated or deaerated. While the reaction can be carried out atany suitable temperature, it proceeds effectively at 50° C. to 100° C.

FIG. 2 schematically shows an organic polymer-metal composite materialaccording to the present invention.

FIG. 2(B) shows the composite material of the invention in which thepolymer of the formula (19) is coordinated with metal atoms M and FIG.2(A) (reference example) shows a composite material in which the polymerof the formula (18) is coordinated with metal atoms M.

As shown in FIGS. 2(B) and (A), the polymers shown by the formulas (19)and (18) can enclose the metal atoms M in their terpyridyl moieties 310.The metal atoms enclosed by the polymer backbone do not cause thebreakdown of the polymer. In particular, when the spacers are arylgroups described in Embodiments 1 and 2, they can readily donate oraccept electrons and allow control of the orientation of the polymer.

The metal atoms have their own electrochemical, spectroscopic andelectromagnetic characteristics. These characteristics are affected bythe polymer shown by the formula (19) or (18) and can therefore becontrolled by introducing proper substituents into the polymer. Whenmoieties having electrochemical, spectroscopic and electromagneticcharacteristics are introduced into the polymer of the formula (19), themetal atoms coordinated with the polymer will interact with thesemoieties. Thus, the characteristics resulting from the polymer may alsobe controlled by the introduction of such moieties.

The above-described polymers may be used as materials to make organicsubstrates to deposit metal materials. Such organometallic compositepolymer materials have novel characteristics and can be used inlight-emitting devices, light-emitting devices, energy-convertingmaterials, drug delivery, sensors, high-performance catalysts, solarbatteries and other technical fields. The monomers described inEmbodiment 1 and Embodiment 2 may be used as starting materials. In sucha case, they may be used in any form and structure and may becopolymerized with other polymers. The monomers may also be mixed withfillers and other materials and shaped into shaped articles.

While examples of the bis-terpyridine monomer of the present inventionwill now be described in the following, it should be appreciated thatthese examples are provided by way of example only and are not intendedto limit the scope of the invention.

Example 1

In a 500 ml flask, terephthal carboxyaldehyde g (3.62 g, 27 mmol), anaryl dialdehyde derivative, was dissolved in an alkaline solutioncomprising calcium hydroxide (3.03 g, 54 mmol) dissolved in water (20ml) and methanol (150 ml). Once terephthal carboxyaldehyde g wascompletely dissolved, 2-acetylpyridine D (6.0 ml, 54 mmol), a2-acetylpyridine derivative, was added and the mixture was stirred atroom temperature for 2 days. After the reaction was completed, theresulting precipitate was collected by suction filtration. The solidproduct was washed with methanol and dried under reduced pressure togive symmetric dienone h (8.09 g, 88% yield).

In a 500 ml flask, the pyridium salt b (7.89 g, 19.5 mmol) and thesymmetric dienone h (3.32 g, 9.74 mmol) obtained in Example 1 were addedto ammonium acetate (37.5 g, 487 mmol) and dehydrated methanol (250 ml).The mixture was refluxed for 12 hours.

Subsequently, the resulting precipitate was collected by suctionfiltration and was washed sequentially with water, methanol and aceticacid. The washed product was extracted with boiling toluene and theextract was concentrated. The resulting solid was recrystallized fromacetic acid and dried under reduced pressure to give dibromobis-terpyridine i (1.36 g, 20% yield). These procedures are shown in thefollowing formula (21):

As in Example 1, the resulting dibromo bis-terpyridine i was identifiedby NMR spectroscopy. The results are shown below.

¹H NMR (CDCl₃) δ≅7.35-7.41 (2H, m), 7.52-7.57 (2H, m), 7.71-7.78 (2H,m), 7.86-7.94 (2H, m), 8.05 (4H, s), 8.62-8.68 (4H, m), 8.74-8.78 (4H,m), 8.79-8.83 (2H, m)

The results indicate that the product was the desired dibromobis-terpyridine.

The dibromo bis-terpyridine i was then subjected to high-resolution massspectroscopy (HRMS). The results are as follows.

The theoretical value for the molecular formula C₃₆H₂₃Br₂N₆ was 679.0345(M+H⁺). The found value was 679.0333 (m/z). Since the difference betweenthe theoretical value and the found value was within the range of error,the product was identified to be the dibromo bis-terpyridine of theforegoing molecular formula.

Several embodiments of the second group of the present invention willnow be described with reference to FIGS. 3 through 15.

Embodiment 1

FIG. 3 schematically shows a polymer material according to Embodiment 1of the second group of the present invention.

As shown by the formula (22) below, the polymer material 100 of thepresent invention includes a bis-terpyridine derivative that serves as aligand, a metal ion and a counter anion. The formula (22) shows arepeating unit 110:

where M is a metal ion; R is a spacer that contains a carbon atom or ahydrogen atom, or directly links the terpyridyl groups to each other;R¹, R², R³ and R⁴ are each independently a hydrogen atom, an aryl groupor an alkyl group; and n is an integer of 2 or greater indicating thedegree of polymerization.

The metal ion is selected from the group consisting of iron ion, cobaltion, nickel ion and zinc ion. Not only can these ions change theirvalency upon oxidation/reduction, but they also have differentoxidation/reduction potentials in the polymer material 100.

The spacer R may be an aryl group or an alkyl group. In this manner, theangle of the terpyridyl group in the polymer material 100 can beadjusted as desired, making it possible to design the polymer material100. The aryl group or alkyl group may further contain an oxygen atom ora sulfur atom. Oxygen atom and sulfur atom are advantageous in designingthe polymer material 100 because of their modification property.

The aryl group is preferably an aryl group selected from the groupconsisting of the formulas (3) through (6) below. Such an aryl groupstructurally defines the skeleton of the ligand and makes it rigid, sothat the polymer material becomes more suitable to make polymer thinfilm.

The counter anion is selected from the group consisting of acetate ion,tetrafluoroborate ion, polyoxometalate and combinations thereof. Such acounter anion compensates for the charge of the metal ion and makes thepolymer material 100 electrically neutral.

When R¹, R², R³ and R⁴ are each an aryl group or an alkyl group otherthan hydrogen atom, examples of such aryl group and alkyl group include,but are not limited to, methyl group, ethyl group, n-butyl group,t-butyl group, phenyl group and tolyl group. The aryl or alkyl group mayinclude additional substituents, including alkyl groups, such as methylgroup, ethyl group and hexyl group, alkoxy groups, such as methoxy groupand butoxy group, and halogen groups, such as chlorine and bromine.

The polymer material 100 exhibits colors such as blue and red aselectrons are transferred between the ligand and the metal ion. Adesired color can be achieved by a proper combination of a ligand and ametal ion since the speed of charge transfer varies depending on thecombination of ligand and metal ion. The speed of charge transfer mayalso be controlled by changing the counter anion.

Specifically, the polymer material exhibits blue or purple color byselecting iron ion as the metal ion and acetate ion as the counteranion. The blue or purple color of the polymer turns deep blue (indigo)by replacing the acetate ion with polyoxometalate. The polymer becomesreddish brown by selecting cobalt ion as the metal ion and acetate ionas the counter anion. By replacing the acetate ion with polyoxometalate,the polymer turns from reddish brown to blue. Since these color changesare dependent upon the speed of charge transfer, it is desirable to knowthe speed of charge transfer for different combinations of metal ion andcounter anion beforehand.

The present inventors have found that controlling the electricalpotential of the polymer material 100 can change the valency of themetal ion and cause oxidation/reduction reactions (thereby causing thepolymer material 100 to exhibit its electrochromic properties). This inturn changes the speed of charge transfer between the ligand and themetal ion and thus brings the polymer material 100 from its coloredstate into its colorless state. In particular, when the counter anion ispolyoxometalate, the polymer material can be readily switched betweenthe colored state and the colorless state since the potential differencerequired for oxidation/reduction reactions can be made large.

Since the polymer material 100 is a polymer electrolyte that candissolve into water, methanol and other solvents, it can be furtherprocessed after its synthesis.

A process for producing the polymer material 100 of the presentinvention will now be described step by step.

Step S110: A bis-terpyridine derivative of the formula (24) and a metalsalt are refluxed in acetic acid and methanol.

In the above formula, R is a spacer that contains a carbon atom or ahydrogen atom, or directly links the terpyridyl groups to each other;R¹, R², R³ and 4 are each independently a hydrogen atom, an aryl groupor an alkyl group; and n is an integer of 2 or greater indicating thedegree of polymerization.

The spacer R may be an aryl group or an alkyl group. The aryl group oralkyl group may further contain an oxygen atom or a sulfur atom. Thearyl group is preferably an aryl group selected from the groupconsisting of the formulas (3) through (6) below. Such an aryl groupmakes the polymer material more suitable to make polymer thin film.

When R¹, R², R³ and R⁴ are each an aryl group or an alkyl group otherthan hydrogen atom, examples of such aryl group and alkyl group include,but are not limited to, methyl group, ethyl group, n-butyl group,t-butyl group, phenyl group and tolyl group. The aryl group or alkylgroup may include additional substituents, including alkyl groups, suchas methyl group, ethyl group and hexyl group, alkoxy groups, such asmethoxy group and butoxy group, and halogen groups, such as chlorine andbromine.

The metal salt comprises a combination of a metal ion, which is selectedfrom the group consisting of iron ion, cobalt ion, nickel ion and zincion, and a counter anion, which is selected from the group consisting ofacetate ion, tetrafluoroborate ion, polyoxometalate and combinationsthereof.

In Step S110, acetic acid and methanol serve as solvents for thebis-terpyridine derivative and the metal salt, respectively. While thereflux may be carried out at a temperature of 150° C. for 24 hours, itmay be carried out under other conditions. Although the conditions forthe reflux vary depending on the spacer and the metal salt selected,those skilled in the art will readily be able to determine suchconditions.

Subsequent to Step S110, the mixture resulting from the reflux may beheated to evaporate the solvents and thus form a powder. This powder iscolored, for example, purple and is in its reduced state. Such powdercan readily dissolve in methanol and is easy to handle.

Embodiment 2

Although Embodiment 1 concerns the case in which the polymer material100 contains a single species of metal ion, the number of metal ionspecies used in the polymer material is not limited according to thepresent invention. In Embodiment 2, a polymer material containing two ormore different metal ion species is described.

FIG. 4 schematically shows a polymer material of Embodiment 2.

As shown by the formula (23) below, the polymer material 200 of thepresent invention includes a bis-terpyridine derivative that serves as aligand, a first to Nth metal ions, and a first to Nth counter anions(where N is an integer of 2 or greater).

In FIG. 4, a unit 210 includes a bis-terpyridine derivative, a firstmetal ion M¹ and a first counter anion, and a unit 220 includes abis-terpyridine derivative, an Nth metal ion M^(N) and an Nth counteranion. In the polymer material 200, the unit 210 and the unit 220 areeach polymerized to a degree of polymerization of at least 2.

In the formula (24), M¹, . . . , M^(N) are first to Nth different metalions, respectively (N is an integer of 2 or greater). R¹, . . . , R^(N)are each independently a spacer that contains a carbon atom or ahydrogen atom, or directly links corresponding terpyridyl groups to eachother (N is an integer of 2 or greater). R¹ ₁, . . . , R¹ _(N), R² ₁, .. . , R² _(N), R³ ₁, . . . , R³ _(N), and R⁴ ₁, . . . , R⁴ _(N) are eachindependently a hydrogen atom, an aryl group or an alkyl group (N is aninteger of 2 or greater). n¹, . . . , n^(N) are each an integer of 2 orgreater indicating the degree of polymerization. First to Nth counteranions may be identical to, different from, or partly identical to oneanother.

The first to Nth metal ions are each selected from the group consistingof iron ion, cobalt ion, nickel ion and zinc ion. Since electricalcharge is transferred at different speeds between the ligand and thedifferent metal ions, these metal ions can cause different colors.

Thus, by combining different metal ions that can cause different colors,the polymer material 200 can be obtained in different colors. It shouldbe appreciated that the first to the Nth metal ions are not limited tothe foregoing metal ions, but may be any combination of metal ions thathave different speeds of charge transfer.

These metal ions also have different oxidation/reduction potentials, sothat a single polymer material 200 can be readily switched betweendifferent colored states and the respective colorless states bycontrolling the electrical potential applied to it.

The spacers R¹, . . . , R^(N) are each an aryl group or an alkyl group.The aryl group or alkyl group may further contain an oxygen atom or asulfur atom. As in Embodiment 1, the aryl group is preferably an arylgroup selected from the group consisting of the formulas (3) through (6)below. Such an aryl group structurally defines the skeleton of theligand and makes it rigid, so that the polymer material becomes moresuitable to make polymer thin film.

The first to the Nth counter anions are each selected from the groupconsisting of acetate ion, tetrafluoroborate ion, polyoxometalate andcombinations thereof. Such a counter anion compensates for the charge ofthe metal ion and makes the polymer material 200 electrically neutral.

When R¹ ₁, . . . , R¹ _(N), R² ₁, . . . , R² _(N), R³ ₁, . . . , R³_(N), R⁴ ₁, . . . , R⁴ _(N) are each an aryl group or an alkyl groupother than hydrogen atom, examples of such aryl group and alkyl groupinclude, but are not limited to, methyl group, ethyl group, n-butylgroup, t-butyl group, phenyl group and tolyl group. The aryl group oralkyl group may include additional substituents, including alkyl groups,such as methyl group, ethyl group and hexyl group, alkoxy groups, suchas methoxy group and butoxy group, and halogen groups, such as chlorineand bromine.

As described above, the polymer material 200 includes the unit 210 thatis polymerized to a degree of polymerization of 2 or more and the unit220 that is also polymerized to a degree of polymerization of 2 or more.Since the polymer material 200 contains different metal ions, it canexhibit different colors based on different speeds of charge transferbetween the metal ions and the ligand. Also, since the metal ions havedifferent oxidation/reduction potentials, the polymer material 200 canexhibit a specific color based on a specific metal ion by controllingthe electrical potential applied to the polymer material. Thus, thepolymer material 200, a single material that can exhibit multiplecolors, helps reduce the time and cost required in the production ofvarious devices. The polymer material 200 is also a polymer electrolytethat can dissolve into water, methanol and other solvents and cantherefore be further processed after its synthesis.

A process for producing the polymer material 200 of the presentinvention will now be described step by step.

Step S210: Each of first to Nth bis-terpyridine derivatives of theformula (25) (N is an integer of 2 or greater) and each of first to Nthmetal salts (N is an integer of 2 or greater) are refluxed in aceticacid and methanol.

In the above formula, R¹, . . . , R^(N) are each independently a spacerthat contains a carbon atom or a hydrogen atom, or directly links theterpyridyl groups to each other (N is an integer of 2 or greater). R¹ ₁,. . . , R¹ _(N), R² ₁, . . . , R² _(N), R³ ₁, . . . , R³ _(N), and R⁴ ₁,. . . , R⁴ _(N) are each independently a hydrogen atom, an aryl group oran alkyl group (N is an integer of 2 or greater). n¹, . . . , n^(N) iseach independently an integer of 2 or greater indicating the degree ofpolymerization.

The spacers R¹, . . . , R^(N) are each an aryl group or an alkyl group.The aryl group or alkyl group may further contain an oxygen atom or asulfur atom. As in Embodiment 1, the aryl group is preferably an arylgroup selected from the group consisting of the formulas (3) through (6)below. Such an aryl group structurally defines the skeleton of theligand and makes it rigid, so that the polymer material becomes moresuitable to make polymer thin film.

When R¹ ₁, . . . , R¹ _(N), R² ₁, . . . , R² _(N), R³ ₁, . . . , R³_(N), R⁴ ₁, . . . , R⁴ _(N) are each an aryl group or an alkyl groupother than hydrogen atom, examples of such aryl group and alkyl groupinclude, but are not limited to, methyl group, ethyl group, n-butylgroup, t-butyl group, phenyl group and tolyl group. The aryl group oralkyl group may include additional substituents, including alkyl groups,such as methyl group, ethyl group and hexyl group, alkoxy groups, suchas methoxy group and butoxy group, and halogen groups, such as chlorineand bromine.

Each of the first to the Nth metal salts comprises a combination of ametal ion, which is selected from the group consisting of iron ion,cobalt ion, nickel ion and zinc ion, and a counter anion, which isselected from the group consisting of acetate ion, tetrafluoroborateion, polyoxometalate and combinations thereof.

In Step S210, acetic acid and methanol serve as solvents for thebis-terpyridine derivative and the metal salts, respectively, as in StepS110 of Embodiment 1. While the reflux may be carried out at atemperature of 150° C. for 24 hours, it may be carried out under otherconditions. Although the conditions for the reflux vary depending on thespacer and the metal salt selected, those skilled in the art willreadily be able to determine such conditions.

Step S220: The first to the Nth reaction products obtained in Step S210are mixed together. The mixing is carried out by stirring the mixture atroom temperature for at least 2 hours. The first to the Nth reactionproducts may be mixed in different proportions or in equal amounts. Asone might expect, the color strength of a specific color can be changedby varying the amounts of the reaction products mixed. As shown in FIG.2, the mixing causes the multiple units 210 and the multiple units 220to bind to one another in a self-aligning manner.

Subsequent to Step S220, the resulting mixture may be heated toevaporate the solvents and thus form a powder. This powder may have amixed color of multiple colors caused by the metal ions in their reducedstate.

The polymer material 200 can be produced in the same manner as in StepS110 of Embodiment 1, except that the metal salts formed with two ormore metal ion species are used. When multiple metal salts are used asstarting materials, the polymer is formed during the reflux so that samespecies of metal ions are arranged in sequence in a self-aligningmanner.

Embodiment 3

Electrochromic devices using the polymer materials 100, 200 obtained inEmbodiments 1, 2 will now be described.

FIG. 5 schematically shows an electrochromic device according toEmbodiment 3.

The electrochromic device 300 includes a first transparent electrode310, a polymer material 320 arranged on the first transparent electrode310 and a second transparent electrode 330 arranged on the polymermaterial 320. The electrochromic device 300 may further include apolymer solid electrolyte 340 arranged between the first transparentelectrode 310 and the polymer material 320.

While the first transparent electrode 310 and the second transparentelectrode 330 may be any transparent conductive film, they arepreferably each an SnO₂ film, In₂O₃ film or an ITO film formed of amixture of In₂O₃ and SnO₂. The first transparent electrode 310 and thesecond transparent electrode 330 may be deposited on a transparentsubstrate, such as a glass substrate, by using any physical or chemicalvapor deposition technique.

The polymer material 320 is the polymer material 100 or 200 described inEmbodiment 1 or 2. The polymer material 320 can be applied on the firsttransparent electrode 310 by spin coating, dip coating or other coatingtechniques.

The polymer solid electrolyte 340 is formed by dissolving an electrolytein a polymer matrix and may contain coloring agents to enhance itscontrast. The coloring agents are not added when the enhancement ofcontrast is not required.

The operation of the electrochromic device 300 is now described.

The first transparent electrode 310 and the second transparent electrode330 are each connected to a power source and apply a predeterminedvoltage to the polymer material 320 and the polymer solid electrolyte340. In this manner, the oxidation/reduction of the polymer material 320can be controlled.

When the polymer material 320 comprises single polymer material 100 ofEmbodiment 1, the polymer material 100 can be switched between itscolored state and colorless state by controlling oxidation/reduction ofthe metal ions in the polymer material 100. When the polymer material320 comprises multiple polymer materials 100 of Embodiment 1, themultiple polymer materials 100 can be individually switched betweentheir colored state and colorless state by individually controlling theelectrical potential applied to the multiple polymer materials 100.

When the polymer material 320 comprises polymer material 200 ofEmbodiment 2, the polymer material 200 can be switched between itscolored state and colorless state by individually controllingoxidation/reduction of the multiple metal ions in the polymer material200. The polymer material 200 of Embodiment 2 is simpler than themultiple polymer materials 100 of Embodiment 1 for use as the polymermaterial 320 since it can be applied in a single coating operation.Multiple devices 300 may be arranged in a matrix pattern.

The second group of the present invention will now be described withreference to Examples 2 and 5, which are not intended to limit the scopeof the present invention.

Example 2

In a 100 ml two-necked flask, 1,4-bis-terpyridine benzene (30 mg, 0.054mmol), a ligand, was dissolved in 25 ml acetic acid by heating thesolution. A solution of iron acetate (9.39 mg, 0.054 mol), a metal salt,in 5 ml methanol was then added to the two-necked flask. The mixture wasrefluxed at 150° C. for 24 hours in a nitrogen atmosphere.

Subsequently, the reaction mixture in the two-necked flask wastransferred to a Petri dish and was dried in the atmosphere to obtain apolymer material as a purple powder (the product is referred to as“FeMEPE,” hereinafter). The yield of the powder was 90%.

Using a cyclic voltameter CV50W, (BAS, Japan), the electrochemicalresponse of FeMEPE was analyzed. For measurement, working electrodeswere prepared by applying a solution of FeMEPE in 20 μl methanol to aglassy carbon electrode (GCE) and an ITO electrode and drying theelectrodes. A Pt counter electrode and Ag/Ag⁺/ACN/TBAP were used as acounter electrode and a reference electrode, respectively. Eachelectrode was manufactured by BAS. A varying voltage of −0.2 V to 1.5 Vwas applied and the analysis was performed at a potential scan rate of0.1 V/s. The results are shown in FIG. 6 and will be described later indetail.

Next, the color changes of FeMEPE were observed visually. Theabove-described ITO electrode was used as a sample. Specifically, avoltage was applied to FeMEPE via the ITO film and the changes in colorwere observed. The results are shown in FIG. 7 and will be describedlater in detail.

Next, the sample used in the visual observation was subjected topredetermined voltages (0 V, 0.8 V and 1.0 V) and analyzed for theUV-visible absorption spectrum in the wavelength range of 400 nm to 800nm using a UV-VIS-NIR spectrometer (UV3150, Shimadzu, Japan) operated ina transmission mode. The results are shown in FIG. 8 and will bedescribed later in detail.

Next, the same sample was analyzed for the speed at which the samplechanges between the colored state and the colorless state, as well asfor the switching characteristic (electrochromic property). As in themeasurement of the UV-visible absorption spectrum, a UV-VIS-NIRspectrometer (UV3150, Shimadzu, Japan) was used to analyze the speed atwhich the sample changes between the colored state and the colorlessstate and the changes in the absorption upon development of color byrepeatedly applying predetermined voltage cycles (0 V and 1.0 V). Theresults are shown in FIG. 9 and will be described later in detail.

Example 3

The same procedure was followed as in Example 1, except that cobaltacetate (9.56 mg, 0.054 mmol) was used as the metal salt. The rest ofthe procedure is the same as in Example 1 and the same description willnot be repeated here. The resulting polymer material is referred to as“CoMEPE,” hereinafter.

As in Example 2, the electrochemical response of CoMEPE was analyzed. Avarying voltage of −0.7 V to 0.8 V was applied and the analysis wasperformed at a potential scan rate of 0.1 V/s. The results are shown inFIG. 10 and will be described later in detail.

As in Example 2, the CoMEPE sample was subjected to predeterminedvoltages (0 V, 0.2 V and 0.4 V) and analyzed for the absorption spectrumin the UV-visible range. The speed at which the sample changes betweenthe colored state and the colorless state as well as the switchingcharacteristic were then analyzed by repeatedly applying predeterminedvoltage cycles (0 V and 0.4 V) to the CoMEPE sample. The results areshown in FIGS. 11 and 12 and will be described later in detail.

Example 4

A solution of FeMEPE (0.5 mg) obtained in Example 1 in methanol (250 μl)was mixed with a solution of CoMEPE (0.5 mg) obtained in Example 2 inmethanol (250 μl). Specifically, the mixture was stirred in a beaker atroom temperature for 2 hours. The resulting mixture is referred to as“CoMEPE-FeMEPE,” hereinafter.

As in Examples 2 and 3, the CoMEPE-FeMEPE was subjected to predeterminedvoltages (0 V, 0.3 V, 0.6 V, 0.8 V and 1.0 V) and analyzed for theUV-visible absorption spectrum in the wavelength range of 420 nm to 780nm. The results are shown in FIG. 13 and will be described later indetail.

As in Examples 2 and 3, the speed at which the sample changes betweenthe colored state and the colorless state as well as the switchingcharacteristic were then analyzed at absorption wavelengths of 520 nmand 580 nm by repeatedly applying predetermined voltage cycles (0 V and1.0 V) to the CoMEPE-FeMEPE sample. The results are shown in FIG. 14 andwill be described later in detail.

Example 5

In a 100 ml two-necked flask, 1,4-bis-terpyridine benzene (60 mg, 0.108mmol), a ligand, was dissolved in 50 ml acetic acid by heating thesolution. A solution of iron acetate (9.39 mg, 0.054 mol) and cobaltacetate (9.56 mg, 0.054 mol), each a metal salt, in 10 ml methanol wasthen added to the two-necked flask. The rest of the procedure is thesame as in Examples 2 and 3 and the same description will not berepeated here. A reddish purple polymer material was obtained (theproduct is referred to as “CoMEPE′-FeMEPE′,” hereinafter).

As in Examples 2 through 4, the CoMEPE′-FeMEPE′ was subjected topredetermined voltages (0 V, 0.6 V, 0.8 V and 1.0 V) and analyzed forthe UV-visible absorption spectrum in the wavelength range of 420 nm to780 nm. The results are shown in FIG. 15 and will be described later indetail.

FIG. 6 is a cyclic voltammogram of FeMEPE.

The ITO electrode and the carbon electrode each showed a current peakindicating oxidation/reduction at 0.77 V.

The peak observed when the potential was scanned from −0.2 V to +1.5 Vindicates oxidation and the peak observed when the potential was scannedfrom +1.5 V to −0.2 V indicates reduction. The oxidation occurs as thevalency of the iron ion in FeMEPE increases from 2 to 3 whereas thereduction occurs as the valency of the iron ion decreases from 3 to 2.

The peak currents indicating oxidation and reduction had the same valuefor each electrode, which demonstrates that the oxidation/reduction ofFeMEPE takes place in a reversible manner. The difference in the peakcurrent between the ITO electrode and the carbon electrode results fromthe difference in the electrode size (surface area). The scanning wasrepeated 500 times, each producing the same result. This suggests thatthe resulting FeMEPE does not fatigue by application of voltage.

FIG. 7 is a diagram showing the color changes of FeMEPE.

In the reduced state, the region 500 was tinted purple (left in FIG. 7).When the FeMEPE was subjected to a potential scan from 0 V to 1.3 V,oxidation occurred at 0.7 V, causing the region 500 to turn from purpleto colorless state (corresponding to region 510) (right in FIG. 7).

When the potential applied to the FeMEPE was again scanned from 1.3 V to0 V, reduction occurred at 0.7 V, causing the material to turn purple(region 500) (left in FIG. 7). Thus, the coloration and discoloration ofFeMEPE was visually confirmed.

FIG. 8 shows absorption spectra of FeMEPE in the UV-visible range.

Based on the results of FIG. 6, voltages of 0 V (reduced state), 0.8 V(oxidation/reduction state) and 1.0 V (oxidized state) were applied. Theabsorption spectrum at 0 V showed a distinct peak at a wavelength of 580nm. This peak indicates the purple color of FeMEPE observed in FIG. 7.The purple color results from the speed of charge transfer from Fe²⁺ ionto the ligand in FeMEPE.

The absorption spectrum at 0.8 V also showed a peak at a wavelength of580 nm, but the peak intensity was lower than that of the absorptionspectrum at 0 V. This is because oxidation took place near 0.8 V, asdescribed with reference to FIG. 6. Specifically, when a voltage of 0.8V is applied to FeMEPE, both Fe²⁺ ion and Fe³⁺ ion are present inFeMEPE. Thus, charge is transferred from Fe²⁺ ion to the ligand at acertain speed, causing the purple color. In the meantime, charge is alsotransferred from Fe³⁺ ion to the ligand at a certain speed. This causesa decrease in the peak intensity of the purple color.

The absorption spectrum at 1.0V did not show absorption at a wavelengthof 580 nm, indicating that the FeMEPE remained colorless without turningpurple. Specifically, when a voltage of 1.0 V is applied, the FeMEPE isin a completely oxidized state in which all iron ions are present in theform of Fe³⁺ ion. Thus, there is no charge transfer from Fe²⁺ ion to theligand that contributed to the purple color, and thus, no color.

These observations suggest that the peak intensity, or the intensity ofthe purple color, of FeMEPE can be varied by controlling the voltage(potential) applied to the FeMEPE. The material can be highly practicalsince it can be controlled by a voltage of about 1 V.

FIG. 9 is a diagram showing the switching characteristic of the peakintensity at a wavelength of 580 nm. The rate constant determined byswitching the applied voltage from 0 V to 1.0 V and measuring the timeit took before the absorbance at 580 nm reached 0 (colorless state) was6.5×10⁻²/s. Likewise, the rate constant determined by switching theapplied voltage from 1.0 V to 0 V and measuring the time it took beforethe absorbance at 580 nm reached a predetermined value (colored state)was also 6.5×10⁻²/s.

This observation also indicates that the coloration and discoloration ofFeMEPE is a reversible process that takes place in a very short periodof time. The speed is comparable to conventional electrochromicmaterials.

The absorbance at 580 nm (thus, the intensity of the purple color) didnot change after the switching of voltage was repeated 500 times,indicating desirable fatigue characteristic.

FIG. 10 is a cyclic voltammogram of CoMEPE.

In FIG. 8, CoMEPE was applied to an ITO electrode. Unlike FeMEPE, acurrent peak indicating oxidation/reduction was observed at 0.20 V. Thepeak observed when the potential was scanned from −0.5 V to +0.3 Vindicates oxidation and the peak observed when the potential was scannedfrom +0.3 V to −0.5 V indicates reduction. As is the case with FeMEPE,the oxidation occurs as the valency of the cobalt ion in CoMEPEincreases from 2 to 3 whereas the reduction occurs as the valency of thecobalt ion decreases from 3 to 2.

The peak currents indicating oxidation and reduction had the same valuefor each electrode, which demonstrates that, like FeMEPE, theoxidation/reduction of CoMEPE also takes place in a reversible manner.It was visually confirmed that CoMEPE was tinted reddish brown in thereduced state and was colorless in the oxidized state.

FIG. 11 shows absorption spectra of CoMEPE in the UV-visible range.

Based on the results of FIG. 10, voltages of 0 V (reduced state), 0.2 V(oxidation/reduction state) and 0.4 V (oxidized state) were applied. Theabsorption spectrum at 0 V showed a distinct peak at a wavelength of 520nm. This peak indicates the visually observed reddish brown color ofCoMEPE. The reddish brown color results from the speed of chargetransfer from Co²⁺ ion to the ligand in CoMEPE.

The absorption spectrum at 0.2 V also showed a peak at a wavelength of520 nm, which was weaker than that of the absorption spectrum at 0 V.This is because oxidation took place near 0.2 V. Specifically, when avoltage of 0.2 V is applied to CoMEPE, both Co²⁺ ion and Co³⁺ ion arepresent in CoMEPE. Thus, charge is transferred from Co²⁺ ion to theligand at a certain speed, causing the reddish brown color. In themeantime, charge is also transferred from Co³⁺ ion to the ligand at acertain speed. This causes a decrease in the peak intensity of thereddish brown color.

The peak intensity of CoMEPE upon oxidation/reduction (at 0.2 V) islower than the peak intensity of FeMEPE upon oxidation/reduction (at 0.8V) described in Example 2 because the color developed by CoMEPE isfainter than the color developed by FeMEPE.

The absorption spectrum at 0.4 V did not show absorption at a wavelengthof 520 nm, indicating that the CoMEPE remained colorless without turningreddish brown. Specifically, when a voltage of 0.4 V is applied, theCoMEPE is in a completely oxidized state in which all cobalt ions arepresent in the form of Co³⁺ ion. Thus, there is no charge transfer fromCo²⁺ ion to the ligand that contributed to the reddish brown color, andthus, no color.

These observations suggest that the peak intensity, or the intensity ofthe reddish brown color, of CoMEPE can be varied by controlling thevoltage (potential) applied to the CoMEPE. In addition, a device thatexhibits different colors can be readily constructed by combining singlelayers of CoMEPE and FeMEPE because of the difference in theoxidation/reduction potential between FeMEPE and CoMEPE.

FIG. 12 is a diagram showing the switching characteristic of the peakintensity at a wavelength of 520 nm. The rate constant determined byswitching the applied voltage from 0 V to 0.4 V and measuring the timeit took before the absorbance at a wavelength of 520 nm reached 0 was2.0×10⁻²/s. Likewise, the rate constant determined by switching theapplied voltage from 0.4 V to 0 V and measuring the time it took beforethe absorbance at a wavelength of 520 nm reached a predetermined valuewas also 2.0×10⁻²/s.

This observation indicates that CoMEPE changes between its colored stateand colorless state at a slower speed than does FeMEPE and there is amargin for improvement in that respect. Nonetheless, that the reversiblecoloration/discoloration of CoMEPE can occur at an oxidation/reductionpotential different from that that causes the color changes of FeMEPEcan be advantageous in designing devices.

The absorbance at 520 nm (thus, the intensity of the reddish browncolor) did not change after the switching of voltage was repeatedmultiple times, indicating desirable fatigue characteristic.

FIG. 13 shows absorption spectra of CoMEPE-FeMEPE in the UV-visiblerange.

The UV-visible absorption spectra of the CoMEPE-FeMEPE were measured byvarying the electrical potential of the material from 0 V (both Co andFe in reduced state), to 0.3 V (Co in oxidation/reduction state, Fe inreduced state), to 0.6 V (Co in oxidized state, Fe in reduced state), to0.8 V (Co in oxidized state, Fe in oxidation/reduction state), and to1.0 V (both Co and Fe in oxidized state). It was visually confirmed thatCoMEPE-FeMEPE turned sequentially from reddish purple, to bluish purple,to blue, and then to colorless state as the potential was varied.

At 0 V, the CoMEPE-FeMEPE developed a reddish purple color. Theabsorption spectrum at 0 V showed distinct peaks at wavelengths of 520nm and 580 nm, which correspond to the peaks of FeMEPE and CoMEPEdescribed with reference to FIGS. 8 and 11, respectively. Thisdemonstrates that Co and Fe are both in their reduced state at thispotential. Having peaks at wavelengths of 520 nm (reddish brown) and 580nm (purple), the CoMEPE-FeMEPE was visually recognized as reddishpurple. These observations suggest that the CoMEPE-FeMEPE containsCoMEPE and FeMEPE as they were produced.

At 0.3 V, the CoMEPE-FeMEPE developed a bluish purple color. Theabsorption spectrum at 0.3 V showed a peak at a wavelength of 520 nmthat was weaker than the corresponding peak observed at 0 V. This isbecause oxidation of Co took place near 0.3 V. On the other hand, thepeak intensity at a wavelength of 580 nm was substantially the same asthat observed at 0 V. These observations suggest that only Co in theCoMEPE-FeMEPE is oxidized at this potential.

At 0.6 V, the CoMEPE-FeMEPE developed a purple color. The absorptionspectrum at 0.6 V had no peak at a wavelength of 520 nm, indicating thatall Co ions in the CoMEPE-FeMEPE are present in the form of Co³⁺ ion. Onthe other hand, the peak intensity at a wavelength of 580 nm wassubstantially the same as those observed at 0 V and 0.3 V.

At 0.8 V, the CoMEPE-FeMEPE developed a purple color. The absorptionspectrum at 0.8 V had no peak at a wavelength of 520 nm, but showed adistinct peak at a wavelength of 580 nm though the peak intensity waslower than those observed in the absorption spectra at 0 V, 0.3 V and0.6 V. This suggests that oxidation of Fe starts near 0.8 V.

At 1.0 V, the CoMEPE-FeMEPE developed a faint purple color. Theabsorption spectrum at 1.0 V had no peak at 520 nm and the absorbance atthis wavelength became substantially 0. On the other hand, the peakintensity at a wavelength of 580 nm significantly decreased as comparedto those observed at 0 V, 0.3 V, 0.6 V and 0.8 V. These observationssuggest that 1.0 V corresponds to the oxidation/reduction potential ofthe CoMEPE-FeMEPE although the oxidation of Fe is not completed evennear 1.0 V.

Since the CoMEPE and the FeMEPE have different oxidation/reductionpotentials, the composite of CoMEPE and FeMEPE can be switched between acolored state and a colorless state for the tints of reddish brown,purple or a mixed color thereof (reddish purple) as desired bycontrolling the electrical potential applied to it.

FIG. 14 is a diagram showing the switching characteristic of the peakintensity at wavelengths of 520 nm and 580 nm.

FIG. 14(A) shows the switching characteristic of the peak intensity at awavelength of 520 nm. The change in the peak intensity at a wavelengthof 520 nm was measured by alternately applying 1.0 V and 0 V to theCoMEPE-FeMEPE. For reference, CoMEPE obtained in Example 2 was alsoanalyzed in the same manner and the results are shown together.

The CoMEPE alone underwent insulation breakdown when 1.0 V was appliedto it. On the other hand, the composite showed electrochromic behaviorwithout undergoing insulation breakdown when 1.0 V was applied. This isconsidered to be because Co becomes more stable when present with Fe.

The rate constant determined by switching the applied voltage from 0 Vto 1.0 V and measuring the time it took before the absorbance at awavelength of 520 nm became minimum (colorless state) was 2.0×10⁻²/s, asdescribed with reference to FIG. 12. Likewise, the rate constantdetermined by switching the applied voltage from 1.0 V to 0 V andmeasuring the time it took before the absorbance at a wavelength of 520nm reached a predetermined value (colored state) was also 2.0×10⁻²/s.This observation indicates that the coloration and discoloration ofCoMEPE-FeMEPE is a reversible process and the composite changes betweenits colored state and colorless state in a similar manner to CoMEPEalone.

The absorbance at a wavelength of 520 nm did not change after theswitching of voltage was repeated multiple times, indicating desirablefatigue characteristic.

FIG. 14(B) is a diagram showing the switching characteristic of the peakintensity at a wavelength of 580 nm. For reference, the results of FIG.9 are shown together. The rate constant determined by switching theapplied voltage from 0 V to 1.0 V and measuring the time it took beforethe absorbance at a wavelength of 580 nm became minimum was 5.0×10⁻³/s.The value was 7.7% of the rate constant of FeMEPE alone, indicating thatiron is oxidized at a slower rate in the composite. This suggests thatthe slight peak at a wavelength of 580 nm in the absorption spectrum ofthe CoMEPE-FeMEPE at 1.0 V (a higher voltage than theoxidation/reduction potential of Fe) shown in FIG. 13 is due to thesignificantly decreased oxidation rate of iron in CoMEPE-FeMEPE. Thereason that the absorbance at a wavelength of 580 nm did not becomecompletely 0 is that the voltage was forcibly switched after 400seconds. It should be noted that had the voltage been applied for alonger period of time, the absorbance would have become 0.

The absorbance at a wavelength of 580 nm did not change after theswitching of voltage was repeated multiple times, indicating desirablefatigue characteristic.

These results demonstrate that the CoMEPE-FeMEPE obtained in Example 4does not comprise randomly arranged CoMEPE and FeMEPE, but rather is ablock copolymer comprising 1,4-bis(terpyridine)benzene, iron and cobalt.

FIG. 15 shows absorption spectra of CoMEPE′-FeMEPE′ in the UV-visiblerange.

The UV-visible absorption spectra of the CoMEPE′-FeMEPE′ were measuredby varying the electrical potential of the material from 0 V (both Coand Fe in reduced state), to 0.6 V (Co in oxidized state, Fe in reducedstate), to 0.8 V (Co in oxidized state, Fe in oxidation/reductionstate), and to 1.0 V (both Co and Fe in oxidized state). It was visuallyconfirmed that, similar to the CoMEPE-FeMEPE of Example 3, theCoMEPE′-FeMEPE′ turned sequentially from reddish purple, to bluishpurple, to purple, and then to colorless state as the potential wasvaried.

Similar to CoMEPE-FeMEPE, the CoMEPE′-FeMEPE′ developed a reddish purplecolor at 0 V. The absorption spectrum at 0 V showed a distinct peak at awavelength of 580 nm and a slight broad peak at a wavelength of 520 nm.

The broad peak at a wavelength of 520 nm and the distinct peak at awavelength of 580 nm correspond to the peaks of FeMEPE and CoMEPEdescribed with reference to FIGS. 8 and 11, respectively. Thisdemonstrates that Co and Fe are both in their reduced state at thispotential.

The reason that the peak at 520 nm is broader than the correspondingpeaks in FIGS. 11 and 13 is that the proportion of CoMEPE present in theCoMEPE′-FeMEPE′ is less than that of FeMEPE.

As in FIG. 13, the CoMEPE′-FeMEPE′, which showed peaks at wavelengths of520 nm (reddish brown) and 580 nm (purple), was visually recognized asreddish purple. These observations suggest that the CoMEPE′-FeMEPE′contains CoMEPE and FeMEPE as they were produced.

At 0.6 V, the CoMEPE′-FeMEPE′ developed a purple color. While theabsorption spectrum at 0.6 V had no peak at a wavelength of 520 nm, theabsorbance did not become completely 0. The reason for this isconsidered to be that although Co ion in the CoMEPE′-FeMEPE′ wasoxidized to Co³⁺ ion, the oxidization rate of Co decreasedsignificantly. On the other hand, the peak intensity at a wavelength of580 nm was substantially the same as that observed at 0 V.

At 0.8 V, the CoMEPE′-FeMEPE′ developed a faint blue color. Theabsorption spectrum at 0.8 V had no peak at a wavelength of 520 nm andthe absorbance became 0 at this wavelength. The peak intensity at awavelength of 580 nm was lower than those observed in the absorptionspectra at 0 V and 0.6 V. This suggests that oxidation of Fe starts near0.8 V.

At 1.0 V, the CoMEPE′-FeMEPE′ was colorless. The absorption spectrum at1.0 V had no peak at a wavelength of 520 nm. The peak at 580 nm was alsosubstantially diminished.

Since the CoMEPE and the FeMEPE have different oxidation/reductionpotentials, the composite of CoMEPE and FeMEPE can be switched between acolored state and a colorless state for the tints of reddish brown,purple or a mixed color thereof (reddish purple) as desired bycontrolling the electrical potential applied to it.

INDUSTRIAL APPLICABILITY

The terpyridine monomer of the present invention has a strong ability tocoordinate with metal atoms. Such a monomer enables design of variousmaterials. Specifically, organic polymer-metal composite materials inwhich the polymer is strongly coordinated with the metal atoms can bereadily prepared from the terpyridine monomer of the present invention.Such composite materials can be used in light-emitting devices,energy-converting materials, drug delivery systems, sensors,high-performance catalysts, solar batteries and other technical fields.

In addition, polymer materials obtained by designing a polymer materialcomprising the terpyridine monomer of the present invention and having aspecific composition and deriving the polymer material can be readilyswitched between a colored state and a colorless state by controllingthe electrical potential applied to it. Such polymer materials can beused in display devices, light modulation devices, electronic papers andother technical fields.

1. A linear electrochromic polymer material comprising first to Nthbis-terpyridine derivatives (N is an integer of 2 or greater), first toNth metal ions (N is an integer of 2 or greater) and first to Nthcounter anions (N is an integer of 2 or greater), the electrochromicpolymer material being represented by the following formula:

where M¹, . . . , M^(N) are first to Nth different metal ions,respectively (N is an integer of 2 or greater); R¹, . . . , R^(N) areeach independently a spacer that contains a carbon atom or a hydrogenatom, or directly links corresponding terpyridyl groups to each other (Nis an integer of 2 or greater); R¹ ₁, . . . , R¹ _(N), R² ₁, . . . , R²_(N), R³ ₁, . . . , R³ _(N), R⁴ ₁, . . . , R⁴ _(N) are eachindependently a hydrogen atom, an aryl group or an alkyl group (N is aninteger of 2 or greater); n¹, . . . , n^(N) are each an integer of 2 orgreater indicating the degree of polymerization; and the first to Nthcounter anions are identical to, different from, or partly equal to oneanother.
 2. An electrochromic device comprising a first transparentelectrode substrate, a second transparent electrode substrate, thepolymer material according to claim 1 arranged between the firsttransparent electrode substrate and the second transparent electrodesubstrate, and an electrolyte arranged between the first transparentelectrode substrate and the polymer material according to claim 1.